It has long been known in the field of disposable absorbent articles that it is extremely desirable to construct absorptive devices, such as disposable diapers, sanitary napkins, incontinence briefs, bandages, wound dressings, and the like, presenting a dry surface feel to the user to improve wearing comfort and to minimize the potential for development of undesirable skin conditions due to the prolonged exposure to moisture absorbed within the article. Accordingly, it is generally desirable to promote rapid fluid transfer in a direction away from the wearer and into a retentive structure, while resisting fluid transfer in the reverse direction.
One viable prior art solution to the aforementioned problem has been to utilize a covering or topsheet on the exposed, wearer-contacting surface of the disposable absorbent article which comprises a nonwoven web. Nonwoven webs formed by nonwoven extrusion processes such as, for example, meltblowing processes and spunbonding processes may be manufactured into products or components of products so inexpensively that the products could be viewed as disposable after only one or a few uses.
Nonwoven webs are often used as topsheets on disposable absorbent articles as they exhibit capillary fluid transport characteristics via the three-dimensional capillaries formed by inter-fiber spaces, thereby conducting fluid away from the wearer-contacting surface and into the underlying absorbent structure. Such nonwoven webs also exhibit an aesthetically-pleasing, cloth-like surface appearance and tactile impression due to their fibrous nature.
While nonwoven webs are effective in transporting fluid, their effectiveness is limited in that such capillary structures can only move fluid once it reaches the capillary interior. Fluid which wets and remains on wearer contacting surfaces contributes to a "wet" tactile feeling or impression, and to the extent that such fluid may be colored or opaque also contributes to a "stained" visual impression. Surface textures naturally occurring in the material of the web or imparted thereto in formation further increase the likelihood that residual fluid will be trapped or retained on the wearer-contacting surface rather than entering capillary structures for transport away from the surface. Thus, surface topographies which contribute to desirable visual and tactile impressions when dry can also tend to retain residual fluid on the exposed surface and thus reduced desirability under in-use conditions.
Accordingly, it would be desirable to provide a nonwoven web with enhanced effectiveness in transporting fluid away from one surface which is initially contacted by a fluid.
More particularly, it would be desirable to retain the visual and tactile properties of nonwoven webs while promoting more rapid and more complete fluid transport away from the wearer-contacting surface and into the interior of an associated absorbent article.
As used herein, the term "nonwoven web", refers to a web that has a structure of individual fibers or threads which are interlaid, but not in any regular, repeating manner. Nonwoven web have been, in the past, formed by a variety of processes, such as, for example, meltblowing processes, spunbonding processes and bonded carded web processes.
As used herein, the term "microfibers", refers to small diameter fibers having an average diameter not greater than about 100 microns.
As used herein, the term "meltblown fibers", refers to fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into a high velocity gas (e.g., air) stream which attenuates the filaments of molten thermoplastic material to reduce their diameter, which may be to a microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers.
As used herein, the term "spunbonded fiber", refers to small diameter fibers which are formed by extruding a molten thermoplastic material as filaments from a plurality of fine, usually circular, capillaries of a spinneret with the diameter of the extruded filaments then being rapidly reduced as by, for example, eductive drawing or other well-known spunbonding mechanisms.
As used herein, the term "elastic", refers to any material which, upon application of a biasing force, is stretchable, that is, elongatable, at least about 60 percent (i.e., to a stretched, biased length, which is at least about 160 percent of its relaxed unbiased length), and which, will recover at least 55 percent of its elongation upon release of the stretching, elongation force. A hypothetical example would be a one (1) inch sample of a material which is elongatable to at least 1.60 inches, and which, upon being elongated to 1.60 inches and released, will recover to a length of not more than 1.27 inches. Many elastic materials may be elongated by more than 60 percent (i.e., much more than 160 percent of their relaxed length), for example, elongated 100 percent or more, and many of these materials will recover to substantially their initial relaxed length, for example, to within 105 percent of their initial relaxed length, upon release of the stretching force.
As used herein, the term "nonelastic" refers to any material which does not fall within the definition of "elastic" above.
As used herein, the term "extensible" refers to any material which, upon application of a biasing force, is elongatable, at least about 50 percent without experiencing catastrophic failure.
As utilized herein, the term "passageway" is intended to encompass enclosed or at least partially enclosed structures or channels which may communicate fluids. The term fluid passageway is thus intended to encompass the terms "aperture", "channel", "capillary", as well as other similar terms.